The twelfth season of Mindcrack Ultra Hardcore is a fight to the death between eight teams of two, similar to season 7. Digging a staircase underground is not allowed; instead players must specifically enter a cave to gather resources.

This was the first season played in vanilla Minecraft, utilizing the /spreadplayers command and the naturalRegenerationgamerule, which had been implemented recently. As a result, brewing potions of regeneration was forbidden.

generikb's footage was accidentally deleted.[9]W92Baj unknowingly didn't record episode 4.[10]PauseUnpause's footage of episode 8 was corrupted.[11]Pakratt0013 released footage of the shenanigans before the intro was recorded, and BlameTC released footage of the teams being organized and given their colors. BlameTC also released footage of post-match discussion, while SethBling included the discussion in his final episode.

Season 12 was marked by the server tick issues that lasted until episode 5. Mobs were extremely fast, the day/night cycle was lasting between 2 and 5 minutes because the sun travelled almost twice as fast. These issues likely contributed to some of the PvE deaths. At the end of episode 5, Guude was made aware of the issues and the server was restarted. Combinations of lag and speed continued into episode 6. Partway through episode 7 the remaining players held a Skype call and decided that the match would be finished out as best it could by going to 0,0, and discussed having a rematch with identical teams. Since the released of season 13, a season 12B is unlikely. The issues were thought to be because of zombie AI tracking.[12]